Loading Geometry

Generally, a reader class is provided for each format. The reader is created, then told to load a file, and it creates a Registry object (see Registry) containing the model. The registry is the final object from a reader, and its top-most volume can be used for visualisation or other operations.

Here, we use example files provided in the g4edge-testdata package that can be installed with:

pip install g4edge-testdata

An instance of the test data can be used to access any file.

GDML

import pyg4ometry
import g4edgetestdata

d = g4edgetestdata.G4EdgeTestData()
r = pyg4ometry.gdml.Reader(d["gdml/ChargeExchangeMC/lht.gdml"])
l = r.getRegistry().getWorldVolume()
v = pyg4ometry.visualisation.VtkViewerColouredMaterial()
v.addLogicalVolume(l)
v.view()

Geant4 example GDML from ChargeExchangeMC example.

FLUKA

Note FLUKA geometry can be loaded but cannot be visualised directly without conversion to a Geant4 model. This is not necessary for simiply loading, but it is shown here.

import pyg4ometry
import g4edgetestdata

d = g4edgetestdata.G4EdgeTestData()
r = pyg4ometry.fluka.Reader(d["fluka/ex-geometry.inp"])
flukaRegistry = r.flukaregistry

geantRegistry = pyg4ometry.convert.fluka2Geant4(flukaRegistry)

l = geantRegistry.getWorldVolume()
v = pyg4ometry.visualisation.VtkViewerColouredMaterial()
v.addLogicalVolume(l)
v.view()

FLUKA example.

ROOT

import pyg4ometry
import g4edgetestdata

d = g4edgetestdata.G4EdgeTestData()
r = pyg4ometry.io.ROOTTGeo.Reader(d["root/lht.root"])
l = r.getRegistry().getWorldVolume()
v = pyg4ometry.visualisation.VtkViewerColouredMaterial()
v.addLogicalVolume(l)
v.view()

ROOT example of Geant4’s LHT geometry.

STL

STL files are typically used for a single watertight solid mesh. This mesh is converted to a TesselatedSolid and then a logical volume which can be placed in a geometry.

import pyg4ometry
import g4edgetestdata

d = g4edgetestdata.G4EdgeTestData()
reg = pyg4ometry.geant4.Registry()
r = pyg4ometry.stl.Reader(d["stl/utah_teapot.stl"], reg)
s = r.getSolid()
copper = pyg4ometry.geant4.MaterialPredefined("G4_Cu", reg)
l = pyg4ometry.geant4.LogicalVolume(s, copper, "utahteapot_lv", reg)
v = pyg4ometry.visualisation.VtkViewerColouredMaterial()
v.addLogicalVolume(l)
v.view()

Example of STL loading in pyg4ometry. Pressing s on the keyboard when in the visualiser will switch to solid mode. w, conversely will switch to wireframe.

STEP

STEP file loading is possible in pyg4ometry. Note, here only a basic loading is shown without material assignment, which normally is not information contained in a STEP file but is necessary for Geant4 or FLUKA simulations.

import pyg4ometry
import g4edgetestdata

d = g4edgetestdata.G4EdgeTestData()
r = pyg4ometry.pyoce.Reader(d["step/1_BasicSolids_Bodies.step"])
ls = r.freeShapes()
worldName = pyg4ometry.pyoce.pythonHelpers.get_TDataStd_Name_From_Label(ls.Value(1))
mats, skip, mesh = {}, [], {}
reg = pyg4ometry.convert.oce2Geant4(r.shapeTool, worldName, mats, skip, mesh)
wl = reg.logicalVolumeDict[worldName]
v = pyg4ometry.visualisation.VtkViewerColouredMaterial()
v.addLogicalVolume(wl)
v.view()

STEP file loading example in pyg4ometry. Pressing s on the keyboard when in the visualiser will switch to solid mode. w, conversely will switch to wireframe.